Although carbon dioxide (CO2) has received the majority of attention related to global warming, methane (CH4) is also a powerful greenhouse gas and its impact on global warming over the last century is equal to about forty percent of the impact of carbon dioxide. In this lecture, Dr. Elaine Matthews, research scientist at NASA's Goddard Institute for Space Science, reveals that seventy percent of global methane emissions each year results from human activities such as rice irrigation, livestock raising, biomass burning, mining and processing of coal, and production and transmission of natural gas and oil. Matthews discusses methane's short lifetime and the implications of the reduction of its sources, which would make a significant impact on the course of global warming.